This invention is related to solid propellants and more particularly to solid propellants which generate nitrogen gas at reduced temperatures.
The production of nitrogen gas is desired for many obvious reasons and applications. One such application is in inflatable devices in which, for safety purposes, it is preferable to accomplish inflation by the use of an inert gas. Nitrogen gas meets this objective. Other similar uses of nitrogen are well known in the art and require no further elaboration.
An especially suitable propellant for generating nitrogen is disclosed in U.S. Pat. application Ser. No. 14,827, filed Feb. 11, 1970, now. U.S. Pat. No. 3,833,432 and incorporated herein by reference. Sodium azide or lithium azide supply the nitrogen for the propellant. A suitable binder is a fluorocarbon. The propellant also contains a combustion catalyst. This propellant produces a very adequate supply of nitrogen and a chamber flame temperature of 2500.degree.F to 4000.degree.F. Such qualities render the propellant especially suitable for pressure feeding of liquid propellant rocket engines due to high gas production. In particular, the gas which is generated by this propellant has a low hydrogen content which renders it suitable for pressurizing an oxidizer system which uses inhibited red fuming nitric acid. When gas having a high content of hydrogen contacts inhibited red fuming nitric acid, undesirable side reactions may result. Thus, the absence of hydrogen in the gas-generating propellant renders it useful to pressurize the oxidizer system. The high flame temperature problem which results in corrosion and destruction of the rocket system is presently overcome by using heavier duty materials. A simpler means for controlling the system is desirable. Reducing the flame temperature is a possible means of eliminating the need for heavy duty material. Reducing the azide content of the propellant reduces the flame temperature. However, the production of reactive hydrogen is increased by this method, thereby causing side reactions in the above-referenced inhibited red fuming nitric acid system. The problem is to reduce the flame temperature which maintaining the desired inert gas analysis produced by the propellant.
A reduced flame temperature with an inert gas analysis makes the propellant suitable for other uses too.
The non-toxic and inert nature of nitrogen also renders it especially suitable for what is known as a man-rated device. A man-rated device provides a great service to man at relatively little danger. For example, the propellant which produces inert gases at a low flame temperature is suitable for use in escape and floatation devices. An inflatable life raft is compact, and the difference between life and death when inflated in an emergency. It is desirable to inflate the raft while minimizing the danger to man.
Because the propellant disclosed in the above-referenced U.S. Pat. application Ser. No. 14,827 filed Feb. 11, 1970, now U.S. Pat. No. 3,833,432 produces a high volume of non-toxic nitrogen gas quickly, it would be an especially suitable propellant for inflating a life-raft or other man-rated device, but the high-chamber flame temperature of 2500.degree.F to 4000.degree.F for the propellant, while perfectly suitable for the rocket applications disclosed therein, creates danger for a man if used in a man-rated device. The need for a nitrogen-producing propellant for use in man-rated devices combined with the knowledge that the above-referenced propellant while suitable for use in rockets also produces a substantial amount of nitrogen leads to a consideration of modifying the rocket propellant for use in a man-rated device, and to reduce flame damage in a rocket.
Reducing the azide concentration of the propellant, reduces the flame temperature which would render the composition suitable for use in a man-rated device where it not for the reduced nitrogen production of the exhaust gas which interfers with the ultimate function of quickly inflating a man-rated device, and were it not for the production of reactive hydrogen which destroys the non-toxic and inert features of the gas produced by the propellant.
The particular binder as disclosed is especially useful for the propellant of the above-referenced patent application. However, some fluorine containing material is produced when the propellant is burned. This fluorine containing material is also toxic. This is another factor to be considered when using the propellant in a man-rated device.
As a consequence, a man-rated gas generator propellant system requiring both low flame temperature (preferably below 1500.degree.F) based on the propellant of the above-referenced application and an inert exhaust is not available due to the fact that the multitude of coolants available from the prior art have not been able to reduce the temperature, maintain the appropriate gas quantities, and maintain the desired inert qualities of the gas at the same time. In other words, it has not been possible to modify the solid gas generating propellant of the above-referenced application of use in man-rated devices.